1. Field of the Invention
The present invention relates to a method of forming an artificial snow surface and an ice crusher machine used in the method. The invention also relates to a method of maintaining a snow surface.
2. Description of the Related Art
According to one conventional method (e.g. the Japanese laid-open utility model gazette No. 63-113866 and U.S. Pat. No. 2,676,471, to be hereinafter referred to as conventional method 1) of forming an artificial snow surface, water and compressed gas ( mainly, air ) both sufficiently refrigerated are sprayed through a nozzle, such that the sprayed mixture is frozen by adiabatic expansion at an atmosphere under the freezing point temperature to be formed into fine ice particles and then the ice particles are accumulated to form a snow surface.
According to another conventional method known from e.g. the Japenese published patent gazette No. 61-31393 (to be hereinafter referred to as the conventional method 2), ice cubes are prepared and these cubes are crushed by means of an ice crusher machine to be rendered into fine ice particles. Then, these particles are sprayed around to be accumulated for forming a snow surface.
According to a still further conventional method known from the Japanese laid-open patent gazette No. 56-133566 (to be hereinafter referred to as the conventional method 3), a weter-receiving bank as an ice-making bank is constructed along a skiing slope. Under a below-freezing point temperature, water is frozen on the ice-making bank to form an ice surface thereon. Then, this ice surface is crushed off by a crusher into fine ice particles and concurrently therewith the ice particles are scattered about onto the skiing slope beside the ice-making bank to form an artificial snow surface.
According to a further conventional method (to be hereinafter referred to as the conventional method 4), an ice layer is formed on a skiing slope by sprinking water under a below-freezing point temperature. Then, the formed ice layer is crushed by means of a roller equipped with a sieving machine driven on the layer to form the layer into fine ice particles.
The Japanese PCT-laid-open patent application No. 62-503118 (PCT/AU86/00158) discloses a still further method (to be hereinafter referred to as the conventional method 5). According to this method, mixture of water and surface-activating agent is stirred to foam. And, this foam is laid out on a skiiing slope to be frozen at a below-freezing point temperature. Thereafter, a roller is driven on the frozen foam in order to crush it into ice particles forming a snow surface.
The above-identified PCT application discloses a further method (to be hereinafter referred to as the conventional method 6). According to this method, the above-described foam generated by stirring the mixture of the water and surface-activating agent is laid out on a flexible grating preliminarily refrigerated by a freezer unit, so that the foam is frozen in the grating. Thereafter, a roller is passed on the frozen foam to crush it into ice particles forming a snow surface.
The above-described conventional methods have drawbacks to be specifically described next.
The conventional method 1 has the significant shortcoming of requiring a great amount of energy for realizing and maintaining the below-freezing point atmosphere regardless of the current climate condition.
The conventional method 2 has the problem of requiring a great amount of labor and costs for the transport of the ice cubes separately prepared.
The conventional method 3 has the problem of requiring a significant amount of space for constructing the water-receiving surface along the skiing slope. The conventional method 4 suffers the problem that the roller often fails to pulvarize the ice layer into sufficiently small particles. Further, if a fine sieve is used to select fine, i.e. good ice particles alone, there will occur a great amount of waste of the unused particles. Conversely, if a rough sieve is used for the sake of economy, there will occur significant quality deterioration, i.e. roughness in the obtained ice particles.
With the conventional methods 5 and 6, the snow surface is formed by pulverizing the frozen foam by means of the roller. Accordingly, the resultant snow surface tends to be too compacted and hard which provides a skier with an uncomfortable and unnatural skiing feel, as compared with a snow surface formed by natural snow.
The conventional method 5 further suffers the same problem of the method 1, i.e. the problem of requring an enormous amount of energy for artificially creating the below-freezing point atmosphere regardless of the natural climate.
Taking the above-described states of the art into consideration, the primary object of the present invention is to provide the method of forming an artificial snow surface with such improvement as to achieve energy, cost and space economies and a snow surface of good quality. The second object of the present invention is to provide a method for effectively maintaining the snow surface formed by the above-described method of the invention. The third object of the present invention is to provide an ice crusher machine useful in the implementation of the invention's method of forming an artificial snow surface.